Lauren Weber’s father is, to put it bluntly, cheap. When she was growing up in the cold winters of Connecticut, he refused to turn the thermostat above 50 degrees. He washed all the dishes by hand, in cold water, even though the family owned a dishwasher. He even used hand motions to signal a turn while driving so his turn-signal bulbs would last longer.

As a kid, Lauren bristled at her dad’s frugality (and when she wanted an extravagance, like Guess jeans, she went to Mom). She feared that her family was secretly on the verge of bankruptcy. They weren’t—her father was, in fact, a professional economist, teaching at the U.S. Coast Guard Academy. He didn’t lack for money. A lifestyle of extreme thrift simply felt right to him.

Then, when Lauren grew up, a funny thing happened: She realized that she’s now cheap, too. And she noticed something else. Her older sister, like her and her father, is very mindful of money. Her older brother is not. Although Lauren carefully compares the prices of dried beans ($1.49 for twelve servings) and canned beans (79 cents for four servings), her brother thinks nothing of eating out all the time. He doesn’t live beyond his means, but he definitely hasn’t adopted the same tightwad attitude that Lauren did.

This scenario might sound familiar to you: One sibling winds up a saver while another is a spender, despite having been raised in the same household. That this happens is not that unusual. What’s interesting is why.

Since the Great Bust began, we’ve heard a lot of talking about thrift. We are, it seems, a nation of newly converted tightwads. Consumer spending has plummeted, the savings rate is going up, and magazines and newspapers have declared this “The New Frugality” as we collectively embrace “The End of Excess.”

Invariably, this conversation is framed in terms of morality. During the boom years, we were reckless. We spent wildly. We were the grasshoppers (Live for today!) and not the ants (Save for tomorrow!). This moralistic attitude toward thrift has a provenance in America. Our puritanical forefathers, from Cotton Mather onward, preached thrift as a virtue, akin to kindness or temperance—a fortifying concept you should choose to embrace.

But what if thriftiness is not a virtue at all? What if being thrifty is not a question of choosing between good and bad behavior but is instead akin to a character trait, like being shy? What if some people are born thrifty and some are not?

Let’s imagine there are four people in a room. The first person is a classically trained economist. The second is Benjamin Franklin. The third is a behavioral psychologist. The fourth person is you. And you are considering the price tag on an expensive pair of boots.

To the economist, your decision to buy the boots should be purely rational. You should think: Do I have the money to afford these boots? If so, is the pleasure they will give me equal to or greater than the cost? And if I save this money, will it afford me greater pleasure in the future—for example, by contributing to a vacation or simply to an increased sense of security?

To Benjamin Franklin, your decision is a moral one. Couldn’t you go another season with your old boots, maybe if you got them resoled? And by denying yourself this indulgence now, might you not become a better person in the long run?

As for the behavioral psychologist, well, until fairly recently, no one was really sure what he would think. While there have been plenty of studies on why we spend money, there have been relatively few studies on why we don’t.

“The standard economic theory says that when we save, we’re making a trade-off between today’s pleasure and tomorrow’s pleasure,” says George Loewenstein, a professor of economics and psychology at Carnegie Mellon University. Yet most of us recognize that decisions about money are rarely that rational. Loewenstein decided to find out why. So, together with Scott Rick of the University of Pennsylvania and Cynthia Cryder of Carnegie Mellon, he completed a study in 2007 in which a group of people—over 13,000 respondents—were given a questionnaire in which they ranked themselves on a “Spendthrift-Tightwad” scale. Then they were presented with several simple spending decisions; for example, they were asked whether, when buying a DVD, they would be willing to pay an extra $5 fee to have it shipped overnight. According to classic economic theory, such a decision should be made through a series of rational considerations, like whether the cost ($5) was worth the benefit (getting the DVD right away). What Loewenstein discovered, however, is that our decisions about money are often driven not by what’s rational but by a purely emotional response that he came to call the “pain of paying.” Simply put, tightwads find spending money painful. Spendthrifts don’t—even if they’re engaging in detrimental behavior, like running up debt. He also discovered a third group: frugal types who find saving money more enjoyable than spending it.